The invention relates to an airbag device for a motor vehicle.
An airbag device of this type comprises an inflatable gas bag; a gas generator for inflating the gas bag; a valve for letting gas out of the (at least partially inflated) gas bag; a moveable actuating element of the valve, which can be actuated in order to open the valve, so that gas can be let out of the gas bag; and a triggering mechanism for actuating the actuating element (to open the valve) by generating pressure.
The inflation of the gas bag by the associated gas generator takes place in the event of a crash in order to reduce the risk of injury to a vehicle occupant. Depending on certain parameters, such as, for example, the size of the vehicle occupant to be protected, the position of the vehicle occupant at the instant of an accident, the relative speed between the occupant and the vehicle as a consequence of an accident and the like, a reduction in the internal pressure of the gas bag compared with the pressure which can be achieved upon full inflation of the gas bag by mechanism of the associated gas generator may be advantageous in order to protect the particular vehicle occupant.
In order to reduce the internal pressure of the gas bag, controlled as a function of the abovementioned parameters, the use of valve arrangements is known, with which gas can be let out of the gas bag to be inflated in a direction away from the vehicle occupant to be protected and can be diverted into a region behind or under the particular airbag module. Contact of the particular vehicle occupant with the possibly hot gases discharging from the gas bag is to be avoided here. The valve arrangement can be opened even before the gas generator is activated, in order right at the beginning of the inflation of the gas bag to provide discharge openings through which gases emerging from the gas generator can flow. By this mechanism, the pressure generated in the gas bag by mechanism of the gas generator is reduced from the beginning. Control of the valve arrangement in such a manner may be particularly advantageous, for example, if it is recognized, by mechanism of a sensor provided for this purpose (for example a weight sensor on a vehicle seat), that the vehicle occupant to be protected is a particularly small, light person.
In the case of an airbag device of the type mentioned at the beginning, which is known from GB 230 64 09 A (which is incorporated by reference herein in its entirety), the actuating element is designed as a rotatably mounted disk which, for actuating purposes, is assigned a pyrotechnically triggerable piston/cylinder unit (in the form of a tappet guided in a cylinder). The piston/cylinder unit in this case is arranged in the plane of the actuating element formed by a rotatable disk and, upon triggering, causes such a rotational movement of the actuating element that through openings provided on the actuating element are brought into overlap with outflow openings of an assigned valve basic body in order to permit the discharging of gas from the gas bag. However, there is the problem here that the space available for the outflow openings is reduced by the space required for the piston/cylinder unit. This is disadvantageous in particular in the case of driver airbag modules, since the modules generally only have a small cross section in the plane perpendicular to the desired gas outlet direction.
The previously described effects also apply to the airbag arrangement known from US Patent Publication No. 2003/0025309A1 (which is incorporated by reference herein in its entirety), in which an actuating element, formed by an annular disk, of a valve of an airbag arrangement is likewise actuated by a piston/cylinder unit.